In manufacturing electronic products, thousands of individual microelectronic devices are generally formed on a single semiconductor wafer or another type of substrate. In a typical fabrication process, one or more thin metal layers are formed on a substrate at various stages of fabricating the microelectronic devices. The metal layers are often applied to the substrate in an electroplating chamber. A typical electroplating chamber includes a bowl or vessel for holding an electroplating solution, one or more anodes in the vessel in contact the electroplating solution, and a substrate holder having a contact ring with multiple electrical contacts that engage a seed-layer on a front surface the substrate. The electrical contacts are coupled to a power supply to apply a voltage to the seed layer. In operation, the front surface of the substrate is immersed in the electroplating solution so that the anode and the seed layer establish an electrical field that causes metal ions in the electroplating solution to plate out onto the seed layer.
As feature sizes continue to shrink, the metal seed layer used to initiate the electroplating process must also be thinner as well. As the seed layer gets thinner it becomes more important that the electrical contacts touching the seed layer are clean and dry. Liquid remaining on the contacts and touching the seed layer has the potential to etch the seed layer. An etched seed layer causes the loss of electrical contact in the etched location which results in an unacceptable electroplated wafer.
In electroplating processors where the contacts are exposed to the plating bath, metal is plated onto the seed layer, and also onto the contacts. The contacts must be frequently “de-plated” to remove the metal that plates onto them. Techniques for deplating contacts have been known and used in the past with varying degrees of success. Still, engineering challenges remain in the design of deplating features in electroplating chambers capable of plating onto ever thinner seed layers.